Molded articles comprising reinforcement fibers and a thermoplastic resin are lightweight and have excellent mechanical properties, and thus have been widely used, for example, in sports applications, aerospace applications, and general industrial applications. As such reinforcement fibers, metal fibers such as aluminum fibers and stainless fibers, inorganic fibers such as silicon carbide fibers and carbon fibers, organic fibers such as aramid fibers and poly p-phenylene benzoxazole (PBO) fibers, and the like are used. From the standpoint of the balance among specific strength, specific rigidity, and lightness, carbon fibers are preferred, and in particular, polyacrylonitrile (PAN) based carbon fibers are preferably used.
The mechanical properties of a carbon fiber reinforced thermoplastic resin molded article can be enhanced, for example, by increasing the amount of carbon fibers, but an increased amount of carbon fibers tends to result in non-uniform distribution of the carbon fibers in the carbon fiber reinforced thermoplastic resin molded article, often causing a reduction in impact strength. Thus, alternatively, the mechanical properties of a carbon fiber reinforced thermoplastic resin molded article can be enhanced, for example, by adding organic fibers having flexibility and high elongation at break in addition to the carbon fibers.
As a composite fiber reinforced thermoplastic resin pellet comprising organic fibers and inorganic fibers that can provide a molded body with high rigidity and high impact resistance, for example, a composite fiber reinforced thermoplastic resin pellet is disclosed, wherein the ratio of organic fibers/inorganic fibers is 1/1 to 1/10; the ratio of thermoplastic resin/reinforcement fibers is 95/5 to 60/40; and the reinforcement fibers are present twisted and substantially aligned along the longer direction of the pellet together with the thermoplastic resin (see, for example, JP 2009-024057 A). Furthermore, as a long-fiber reinforced composite resin composition having high mechanical strength and provided with conductivity, a long-fiber reinforced composite resin composition comprising an olefin resin, organic long fibers, and carbon fibers is disclosed (see, for example, JP 2009-114332 A). Unfortunately, molded articles obtained using these techniques are still poor in impact strength and low-temperature impact strength.
As a resin composition having fuel barrier properties consistent with impact resistance, a resin composition is disclosed, comprising a mixture of a thermoplastic resin and 4- to 20 mm-long fibers having a melting point higher than that of the thermoplastic resin or being infusible (see, for example, US 2006/068141 A1). Unfortunately, molded articles obtained using such a technique are poor in mechanical properties, particularly, impact strength and low-temperature impact strength.
Thus, it is desirable to develop, by a convenient method, a fiber reinforced thermoplastic resin molded article comprising a thermoplastic resin as a matrix, which is excellent in mechanical properties, particularly, impact strength and low-temperature impact strength, and can exhibit high impact properties.